Terbium (Tb)


  • Symbol: Tb
  • Atomic Number: 65
  • Atomic Weight: 158.92535
  • Element Classification: Lanthanide
  • Discovered By: Carl Gustaf Mosander
  • Discovery Date: 1843
  • Name Origin: Named after Ytterby, a village in Sweden, where its ore was mined
  • Density(g/cc): 8.23
  • Melting Point: 1356°C
  • Boiling Point: 3230°C
  • Appearance: Silvery-white, malleable, ductile, and soft metal
  • Atomic Radius(pm): 177


Terbium was discovered by Swedish chemist Carl Gustaf Mosander in 1843. Mosander was able to isolate terbium as a new element from a mineral that was later named gadolinite, from the Ytterby mine in Sweden, where several other rare earth elements were also discovered. The name “terbium” is derived from Ytterby, reflecting the element’s connection to the location of its discovery. Initially, terbium was confused with other rare earth elements due to their similar properties and the difficulty in separating them.

Relation to Other Elements

Terbium is part of the lanthanide series, which includes elements with atomic numbers from 57 (lanthanum) to 71 (lutetium). Like other lanthanides, terbium is characterized by its trivalency, although it can also exhibit a +4 oxidation state in some compounds. Terbium’s properties are similar to those of its lanthanide counterparts, including its reactivity with water, formation of stable compounds, and usefulness in various technological applications due to its magnetic and luminescent properties.

Natural Occurrence

Terbium is not found free in nature but occurs in small amounts in several minerals, including monazite and bastnasite, which are rich in rare earth elements. The extraction and purification of terbium from these minerals are complex, requiring sophisticated separation techniques due to the close chemical similarities among the lanthanides.


Terbium has several specialized applications:

  • Magnets: Terbium is used in the production of terbium-doped strontium barium manganite, a material with magneto-optical properties used in the construction of data storage devices and magneto-optical disks.
  • Solid-State Devices: Terbium-doped calcium fluoride and other compounds are used in solid-state devices, including sensors and actuators, due to their unique luminescent and magnetic properties.
  • Phosphors: Terbium is an important component in green phosphors used in color television tubes, fluorescent lamps, and LED lights, providing bright, efficient green light.
  • Lasers: Certain terbium compounds are utilized in lasers and other devices that require materials with specific optical properties.

The discovery of terbium, along with other rare earth elements from the Ytterby mine, significantly contributed to the development of modern electronics and lighting technologies. Despite its relatively low abundance, terbium’s unique properties make it invaluable for specific high-tech applications, particularly where its luminescent and magnetic characteristics are required.

Gadolinium (Gd)

Dysprosium (Dy)